1. Field of the Invention
This invention relates generally to the art of cold forming teeth on a workpiece and, more particularly, to a novel and improved roll-through cold forming apparatus. The invention is specifically concerned with a non-generating teeth forming apparatus for simultaneously forming a plurality of either external or internal straight spline or gear type teeth, on a cylindrical workpiece, by operatively engaging the workpiece with tooth forming edges on a plurality of teeth forming members disposed radially about said workpiece during movement of the workpiece past the teeth forming members.
2. Description of the Prior Art
It is well known in the art of cold forming teeth on the periphery of a workpiece to employ a plurality of non-generating, pivotally mounted tooth forming blades which are readily disposed around a workpiece and which are power actuated into engagement with the workpiece during a tooth forming operation. An example of such a prior art apparatus for cold forming teeth on the periphery of a workpiece is disclosed in prior U.S. Pat. No. 3,396,570 to McCardell.
A disadvantage of the tooth forming apparatus disclosed in the McCardell patent is that the teeth are formed in a workpiece by parallel forming instead of radial forming as in the present invention. That is, in forming teeth with the McCardell apparatus, each of the tooth forming blades has a parallel tooth forming edge on the workpiece engaging end thereof, and there is relative movement between the workpiece and each of the tooth forming edges which provides a great deal of sliding friction during a parallel tooth forming operation. Accordingly, in the parallel tooth forming method carried out by the McCardell apparatus, there is a high percentage of total tooth forming action in the last few degrees of rotation of each of the powered tooth forming blades, as for example, in the last ten to fifteen degrees of rotation of the blades.
The aforedescribed sliding, parallel tooth forming apparatus creates extremely high forces, both in the overall machine and in each of the tooth forming blades, as well as in the workpiece. One injurious result of said high forces created in the workpiece is that, due to the metal forming being carried out in a short time period, there is a great deal of metallurgical destruction done to the workpiece. The formation of extremely high forces created on the forming machine are incurred in the various parts thereof, which results in deflections in the machine parts, and inaccuracies in the final workpiece. In order to resist such high forces created during the forming action of the McCardell apparatus, the apparatus must have an inherent strength to resist such forces, which means increased weight and manufacturing costs in the various parts of the McCardell machine, as for example, in the transmission and drive train.
It is also well known in the prior art to form teeth on the exterior of a workpiece by providing a plurality of multiple forging or striking type tooth forming tool members which are driven in a direction perpendicular to the external side of a stationary workpiece, so as to progressively form the depth of a tooth in the external side of a workpiece. The metal in the workpiece is worked at a slower rate than in the aforementioned McCardell apparatus, but the continual hammering or kneading type effect produced by the forging type prior art machine creates the problem of workpiece hardening as such forming operation is carried out.